problems with verilog SDRAM models

[wallge]

I am trying to write an SDRAM controller in VHDL for a mobile SDR SDRAM
that I want to be able to control via an FPGA on the same PCB.
I am having trouble with the verilog model. I have used both a samsung
and a micron model for the part (two compatible parts). Unfortunately
these models are not available in VHDL, and my verilog is pretty weak.

I wondered if any one had some experience with memory models, both in
terms of using them to design memory controllers and debugging them
when they spit out spurious timing violations.
These verilog models in particular seem to send out all manner of
timing violations or functional problems that don't seem to be in line
at all with what the data sheet says regarding the timing and command
and control procedures (for doing a full page read or write, for
instance).

Has any one else had trouble with bad/buggy models? What is the best
way to solve this problem?
What is the best way to go about designing a memory controller (I have
seen an example on Altera's website in VHDL (but it sucks), as well as
some others in open cores and one written for a homebrew graphics
accelerator card (manticore). I find the documentation and/or
functionality lacking in most of the aforementioned existing reference
designs.

thanks

 

[ghelbig]

In my experience, the Micron models are very very good. I did find a
subtle bug in one of their DDR SDRAM models, but it did not affect
normal behaviour, and they fixed it as soon as it was brought to their
attention.

There are SDR SDRAM VHDL models available from Micron. The differences
between one 4-band SDRAM and another 4-bank SDRAM are mote, so just
pick one and go with it.

GH

 

[Amirtham]

In my experience, the Micron models are very very good. I did find a
subtle bug in one of their DDR SDRAM models, but it did not affect
normal behaviour, and they fixed it as soon as it was brought to their
attention.

There are SDR SDRAM VHDL models available from Micron. The differences
between one 4-band SDRAM and another 4-bank SDRAM are mote, so just
pick one and go with it.

GH

currently I m doing the interface between SDRAM and FPGA. but
Controller is using VHDL. I have written my own code refering to a
couple of verilog cores. I am facing problem in accessing another bank
of same row simultaneuosly.
I require a page burst of more than the columns available in single
bank. Help me pls if you can.

thanks,
MDA.

 

[helmut.leonhardt]

Hi,

you can try to finde any equivalent models at hynix or quimonda (former
infinion).
Or use freemodelfoundry.com. I had the same problem, because Xilinix
Memory Interface Generator also provided verilog only models.

Bye Helmut

 

[helmut.leonhardt]

You can also look here:

http://groups.google.com/group/comp...4ced2/c2cc389ee809ce7d?hl=en#c2cc389ee809ce7d

Bye Helmut

 

[Niv]

I am trying to write an SDRAM controller in VHDL for a mobile SDR SDRAM
that I want to be able to control via an FPGA on the same PCB.
I am having trouble with the verilog model. I have used both a samsung
and a micron model for the part (two compatible parts). Unfortunately
these models are not available in VHDL, and my verilog is pretty weak.

I wondered if any one had some experience with memory models, both in
terms of using them to design memory controllers and debugging them
when they spit out spurious timing violations.
These verilog models in particular seem to send out all manner of
timing violations or functional problems that don't seem to be in line
at all with what the data sheet says regarding the timing and command
and control procedures (for doing a full page read or write, for
instance).

Has any one else had trouble with bad/buggy models? What is the best
way to solve this problem?
What is the best way to go about designing a memory controller (I have
seen an example on Altera's website in VHDL (but it sucks), as well as
some others in open cores and one written for a homebrew graphics
accelerator card (manticore). I find the documentation and/or
functionality lacking in most of the aforementioned existing reference
designs.

thanks

Hi, I'm trying to use an AMD (Spansion) FLASH model, and it's just one
BIG headache.
Despite following all their advice and recompiling lots of libraries
with vital2000, the model
still falls over immediately in modelsim.

It's really poor putting out models that just don't work, IMO.

Kev P.

 

[Brian Drummond]

I am trying to write an SDRAM controller in VHDL for a mobile SDR SDRAM
that I want to be able to control via an FPGA on the same PCB.
I am having trouble with the verilog model. I have used both a samsung
and a micron model for the part (two compatible parts). Unfortunately
these models are not available in VHDL, and my verilog is pretty weak.

Micron certainly used to provide good VHDL models, and I wish they still
did. Look for an older non-mobile equivalent for the SDRAM (same size,
bus width, banks, etc and same speed grade if possible) and you'll
probably find a VHDL model for it.

Failing that, Hynix provide VHDL models, but I don't know if they have
an equivalent part to the mobile SDRAM you are using.

- Brian

 

[FMF]

Kev,

Please contact me through the FMF website. We have received no bug
reports on this model. Although the VITAL2000 issue is common, it is
limited to modelsim. I will help you workout whatever other issues you
have. If there is an actual bug, we are under contract from Spansion to
fix it.

Rick Munden

 

[FMF]

What partnumber do you need to simulate?

 

[Kevin Neilson]

I am trying to write an SDRAM controller in VHDL for a mobile SDR SDRAM
that I want to be able to control via an FPGA on the same PCB.
I am having trouble with the verilog model. I have used both a samsung
and a micron model for the part (two compatible parts). Unfortunately
these models are not available in VHDL, and my verilog is pretty weak.

....

I used a Verilog Micron model to develop my DDR/DDR2 controller and was
very happy with the model. I had to set a couple of `defparams to make
the model match my hardware, and it was very helpful in reporting all
timing errors, such as violations in write recovery time, etc. There is
a "Debug" parameter you can switch on to report all data transactions as
well. Before you write your own controller, though, I warn you that it
is much more difficult than you anticipate. -Kevin